The following videos will help you get the lay of the land of the Design System and Sketch for Teams.
VA.gov Design System
This video will show you how to contribute to the design system and walk through the content style guide, foundational elements, components, and patterns.https://youtu.be/gnREjK1AmxE
Sketch for Teams
This video walks through how to find and add the VA.gov Design System library to Sketch and an annotations library to create accessibility annotations for your mock-ups.https://youtu.be/nhpZbSY8OG0